Nick Roach grew up drawing pictures and went on to earn a degree in art theory and practice at Northwestern. He's always working on a sketch in his mind, and the one of his budding football career is finally ready to hang on the wall. Seven years along, the last details and shadings are becoming clear as he leads a resurgent Raiders defense.

Oakland, which hosts Philadelphia (3-5) Sunday, is a surprising 3-4 largely on the back of its defense. Safety Charles Woodson is the one star, but the other pistons have been firing pretty well, too - and Roach, the once-undrafted middle linebacker, is the fuel and air.

Roach calls the plays, and he is adept at both run defense and pass coverage.

"He is the leader of the defense," defensive end Lamarr Houston said. "He runs the whole machine. He is the guy behind the curtains, and he never shies away from it."

The Raiders, sixth in the NFL in run defense, have held three opponents under 40 yards rushing after doing that just four times in the previous 10 seasons. Oakland also blitzes often and from everywhere, and already has 21 sacks after having 25 all of last season.

The biggest difference is Roach - and the guy he replaced. Rolando McClain, the Raiders' first-round pick in 2010, was supposed to be everything Roach is now, only in a bigger package. But McClain struggled on the field and was often in trouble off it. The Raiders have 10 new starters on defense now, and the one holdover, Houston, acknowledged the importance of the McClain-to-Roach transition.

"It is different, it is," Houston said. "That was the point of them going out and getting guys that will fit in and do what they're supposed to, understand what they're supposed to do and how they're supposed to do it.

"That's a testimony to (general manager) Reggie McKenzie and (coach) Dennis Allen as to how they put this team together."

Roach got a four-year contract on a defense largely consisting of one-year free agents. He wasn't daunted by the task of strangers coming together to play defense, taking a direct, humble, hardworking approach at training camp. Roach admitted his mistakes and implored teammates to grow together.

"Defense isn't about how many guys have been together before," Roach said. "It's just if guys have played good football before. Guys wanted to win, and that was the foundation."

Roach has spent seven years building his own foundation, going from an undrafted player out of Northwestern to the Chargers' practice squad in 2007 before getting picked up by the Bears.

He was a backup, an outside linebacker and a middle linebacker when Brian Urlacher was hurt. Then he packed up the RV and headed west when Oakland signed him this offseason.

McKenzie, Allen and defensive coordinator Jason Tarver loved Roach's understated approach, intelligence and underrated playmaking ability. The one question mark was if Roach was, at 6-foot-1, 234 pounds, a bit undersized for a middle linebacker, but Tarver shook his head.

"Undersized is one thing, and the ability to get off the block is another," Tarver said. "Nick knows how to use his hands and has long arms for his body.

"You can look at the guys I was around before, Patrick Willis and NaVorro Bowman - Nick is a little bit lighter than those guys, but they're similar in arm length so they can shed and get off blocks."

Roach was a running back in high school, and can still find the open space as a linebacker.

"He's been a pleasant surprise," former Eagles scout and radio analyst John Middlekauf said. "He was a demon on special teams when we used to play the Bears, and now he is a consistent, efficient tackler."

Roach has a team-high 39 tackles, according to Pro Football Focus, to go along with a sack, eight quarterback hurries and two forced fumbles.

"We put a lot on him," Allen said. "He's accepted that challenge, and I think he's been an outstanding player for us."

He's also been a mentor to rookie outside linebacker Sio Moore, who credits his 2.5 sacks in the past two games to talks with Roach. Roach showed him a more-detailed note-taking approach to watching game film and has been in his ear when Moore has typical rookie frustrations.

"He's teaching me how to be a better pro and a better person," Moore said. "I am more focused, and it's paying off on game day."

Roach deflects a lot of the praise from coaches and teammates. He'll even wince if you call him the backbone of the defense.

"I get a lot more credit than I deserve on that front," Roach said. "There are 11 guys out there, 11 guys going crazy. For me to get the credit is a little much. Once I make the defensive call, they do what they do."

It's an important job getting guys in the right spot.

"But they have an important job too," Roach said.

The Raiders don't seem to have any players this year "who are all about themselves," Roach said. But Tarver said Roach deserves credit for that, too.

"He is such a good communicator and is so good with the guys," Tarver said. "He's very intelligent. There is nothing that Nick Roach can't do in football or in life."

Well, he doesn't paint. Doesn't have the patience. And he doesn't draw as much as he used to. Now, he grabs the camera and goes on road trips with his pregnant wife, Anna-Marie, and their three dogs.

"We love it here," Roach said. "She has family here. The weather is great, we love going on hikes. And taking a lot of pictures."

The Raiders' picture is definitely more in focus and brighter than a year ago, thanks to the artist in the middle.

"It's different," Tarver said. "You point the players in the right direction, and they learn and they go. And Nick is right in the center of that."

Eagles (3-5) at Raiders (3-4)

When: 1:05 p.m. Sunday. TV/Radio: Channel: 2 Channel: 40 / 95.7

Spotlight on: Raiders QB Terrelle Pryor. When he was at Oregon, Eagles coach Chip Kelly tried to recruit Pryor - and the former college coach would probably love to have him now for the wide-open, up-tempo spread offense he is using in Philadelphia. Pryor had a 93-yard touchdown run last week and leads all NFL QBs with 391 yards rushing.

Back in action: Eagles QB Nick Foles has completed 52 of 90 passes for 622 yards and six touchdowns with no interceptions. He was 22-of-31 for 296 yards with three touchdowns against Tampa Bay, but completed only 11 of 29 attempts for 80 yards against Dallas a week later. He suffered a concussion in that game and sat out last week.

First-half heroes: Oakland has outscored opponents 59-20 while averaging 196.3 yards over the first 30 minutes in its past four games. The Raiders have lost the second half 63-10 and generated just 91.3 yards on average.

Strong defense: Philadelphia has not allowed a 100-yard rusher and held its past four opponents under 100 yards rushing total. Oakland RB Darren McFadden is coming off his first two-touchdown game since 2011.